Cartridge block for multilayer ceramic screening

ABSTRACT

An assembly for screening a multilayer ceramic with a conductive paste includes a paste cartridge containing the conductive paste; a cartridge block, a top of a cartridge block being configured to receive the paste cartridge, the cartridge block comprising a paste routing section, the paste routing section comprising a flared section located at a bottom of the cartridge block; a pneumatic fitting attached to the paste cartridge, the pneumatic fitting configured to pressurize the conductive paste in the paste cartridge such that the conductive paste is extruded from the paste cartridge into the cartridge block through the paste routing section of the cartridge block by the pressure from the pneumatic fitting; and a nozzle connected to the flared section of the cartridge block, the nozzle configured to receive the conductive paste from the flared section, and screen the conductive paste onto the multilayer ceramic through the nozzle.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. application Ser. No. 12/938,408(Harkins et al.), filed on Nov. 3, 2010, which is herein incorporated byreference in its entirety.

FIELD OF INVENTION

This disclosure relates generally to the field of multilayer ceramicscreening.

DESCRIPTION OF RELATED ART

Multilayer ceramic (MLC) semiconductor packages are formed by stackingand bonding together flexible paperlike sheets commonly referred to asceramic green sheets. Green sheet segments of desired size andconfiguration are punched to provide via holes and, by a screen printingtechnique, a conductive paste (which may be a copper paste) fills thevia holes and/or a conductive circuit pattern is applied to the face ofthe green sheet as required. Such green sheets, after screening, areassembled in a stack, pressed, and subsequently sintered in an oven at arelatively high temperature. Upon sintering, the vehicle and any bindermaterial are burned off with the remaining rigid unitary ceramic bodyprovided with interior interconnected conductive patterns. Additionalprocessing occurs prior to the units being encapsulated.

Critical to the MLC manufacturing process is the screening operation.Screening is performed by extruding the paste from a paste tube though ametal mask to create the circuit pattern lines and to fill vias in thegreen sheets. The ceramic green sheets are relatively fragile, with athickness that may be on the order of 0.008 inches, and a surface areathat is relatively large compared to the thickness. Particular problemsare encountered when screening such relatively soft and deformable,paper-thin, flexible green sheets, which are of no concern to thegeneral screen printing art utilizing rigid substrates. Also, theconductive pastes used for MLC screening may be difficult to work with,thus complicating the screening process itself.

The conductive paste may be stored in cylindrical plastic pastecartridges after manufacture. The paste is then transferred from thepaste cartridge to a specialized screening paste tube via paste transfertooling in order to perform the screening process by extrusion of thepaste from the tubes. This requires both specialized, complex pastetransfer tooling, and a time-consuming transfer process to fill thepaste tubes from the plastic cartridges. Once the paste tube is filledwith the paste, the loaded paste tube is installed on a screening toolfor the screening of greensheets. The paste tubes are mechanicalassemblies that include many components, including a paste reservoir,shutter, shutter arms, shutter cylinder, plunger T-bar and a tefloninsert. The reservoir section of a filled paste tube has a rectangularcross-section topped by a plunger T-bar with a teflon insert andfinished at the bottom with a carbide rod nozzle through which screeningis performed. Systems and methods for screening of greensheets usingsuch paste tubes are discussed in further detail in U.S. Pat. No.4,362,486 (Davis et al.), issued on Dec. 7, 1982 and assigned toInternational Business Machines Corporation, which is hereinincorporated by reference in its entirety.

The paste tubes have several high wear components which may drive up thecost of the screening process, including the teflon insert, shuttercylinder, and shutter. The paste tubes are also relatively difficult toclean, requiring specialized cleaning tools and high temperature, highpressure cleaning chemicals. The paste tubes must be broken down intomany parts prior to cleaning, and must be rebuilt after cleaning by acertified operator. The paste tubes must be broken down and cleanedfrequently to ensure proper operation of the screening process, due tothe many moving parts included in the paste tubes. The frequency andcomplexity of the paste tube cleaning process, in addition to thetransfer of the paste from the paste cartridges to the paste tubes,reduces the overall throughput of the MLC screening process.

SUMMARY

In one aspect, an assembly for screening a multilayer ceramic with aconductive paste includes a paste cartridge containing the conductivepaste; a cartridge block, a top of a cartridge block being configured toreceive the paste cartridge, the cartridge block comprising a pasterouting section, the paste routing section comprising a flared sectionlocated at a bottom of the cartridge block; a pneumatic fitting attachedto the paste cartridge, the pneumatic fitting configured to pressurizethe conductive paste in the paste cartridge such that the conductivepaste is extruded from the paste cartridge into the cartridge blockthrough the paste routing section of the cartridge block by the pressurefrom the pneumatic fitting; and a nozzle connected to the flared sectionof the cartridge block, the nozzle configured to receive the conductivepaste from the flared section, and screen the conductive paste onto themultilayer ceramic through the nozzle.

Additional features are realized through the techniques of the presentexemplary embodiment. Other embodiments are described in detail hereinand are considered a part of what is claimed. For a better understandingof the features of the exemplary embodiment, refer to the descriptionand to the drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Referring now to the drawings wherein like elements are numbered alikein the several FIGURES:

FIG. 1 illustrates a cross-section an embodiment of a cartridge blockfor MLC screening.

FIG. 2 illustrates a side view of the cartridge block for MLC screeningof FIG. 1.

FIG. 3 illustrates a top view of the cartridge block for MLC screeningof FIG. 1.

FIG. 4 illustrates a bottom view of the cartridge block for MLCscreening of FIG. 1.

FIG. 5 illustrates an embodiment of a cartridge block and a pastecartridge attachment nipple for MLC screening.

FIG. 6 illustrates an embodiment of an MLC screening assembly includinga cartridge block, paste cartridge, pneumatic fitting, and nozzle.

FIG. 7 illustrates an embodiment of a method of MLC screening using acartridge block and a paste cartridge.

DETAILED DESCRIPTION

Embodiments of a cartridge block for MLC screening and a method of MLCscreening using a cartridge block are provided, with exemplaryembodiments being discussed below in detail. An MLC screening paste tubemay be replaced with a cartridge block assembly that allows the paste tobe extruded directly from the paste cartridge in which the paste isstored through the cartridge block to a nozzle through which MLCscreening is performed. Therefore, there is no need to transfer thepaste from the paste cartridge into a paste tube before screening.

The cartridge block may be relatively easy to clean, using, for example,wipes and isopropyl alcohol. No specialized, high cost cleaning tools orhigh temperature, high pressurized cleaning chemicals may be required.The cartridge block has relatively few components, which maysignificantly reduce breakdown, rebuild, and maintenance time needed forthe cartridge block assembly versus the paste tube. Further, thecartridge block may be used for more screening processes before needingto be broken down and cleaned as compared to the paste tube.

FIG. 1 illustrates a cross-section 100 of an embodiment of a cartridgeblock. Threaded cartridge attachment 102 is located at the top of thecartridge block body 101 in a recessed area 105. Below threadedcartridge attachment 102 is a paste routing section, including a hole103 and beveled flared section 104. In operation, paste is forcedthrough hole 103 and flared section 104 from threaded cartridgeattachment 104. Flared section 104 causes the paste to flare out, tofully cover the surface of a nozzle attached to the cartridge block atthe flared section (discussed further below with respect to FIG. 6). Thecartridge block body 101 may have a height (indicated by line 106) ofapproximately 3.375″ and a length (indicated by line 107) ofapproximately 8.5″. A top angled portion of the flared section 104 mayhave a height (indicated by line 108) of approximately 0.15″, and abottom vertical portion of the flared section 104 may have a height(indicated by line 109) of approximately 0.1″. The hole 103 may beround, with a diameter (indicated by line 110) of approximately 0.25″.Dimensions 106-110 are given for illustrative purposes only; a cartridgeblock body 101 may be any appropriate size. The cartridge block body 101may be made from a metal such as stainless steel in some embodiments,and the paste routing section, including hole 103 and beveled flaredsection 104, may be formed by milling the cartridge block body 101.

FIG. 2 illustrates a side view 200 of the cartridge block of FIG. 1. Thecartridge block body 101 may have a top width (indicated by line 201) ofapproximately 1.5″, a height (indicated by line 202) of approximately3.375″, and a bottom width (indicated by line 203) of approximately0.96″. Dimensions 201-203 are given for illustrative purposes only; acartridge block body 101 may be any appropriate size.

FIG. 3 illustrates a top view 300 of the cartridge block of FIG. 1.Cartridge block body 101 surrounds recessed area 105 and threadedcartridge attachment 102. The hole 103 is visible through the threadedcartridge attachment 102. The cartridge block body 101 may have a topwidth (indicated by line 301) of approximately 1.5″, and a top length(indicated by line 302) of approximately 9″. Dimensions 301-302 aregiven for illustrative purposes only; a cartridge block body 101 may beany appropriate size.

FIG. 4 illustrates an embodiment of a bottom view 400 of the cartridgeblock of FIG. 1. Cartridge block body 101 surrounds the flared section104, and hole 103 is visible through flared section 104. The cartridgeblock body 101 may have a bottom width (indicated by line 402) ofapproximately 0.96″, and a bottom length (indicated by line 403) ofapproximately 8.5″. The flared section 104 may have a width (indicatedby line 404) of approximately 0.25″, and a length (indicated by line401) of approximately 8.0″. The length 401 and width 404 of flaredsection 104 may be determined by the dimensions of a nozzle that isattached to flared section 104 and used for the MLC screening process(discussed further below with respect to FIG. 6). Hole 103 may have adiameter of approximately 0.25″. Dimensions 401-404 are given forillustrative purposes only; a cartridge block body 101 may be anyappropriate size.

FIG. 5 illustrates an embodiment of an assembly 500 including a crosssection of a cartridge block 501 and a paste cartridge attachment nipple503. The bottom of paste cartridge attachment nipple 503 is configuredto attach (e.g., screw in) to threaded cartridge attachment 504 incartridge block 501, and the top of paste cartridge attachment nipple503 is configured to attach (e.g., screw in) to a paste cartridge.Cartridge block 501 also includes a paste routing section including hole505 and flared section 506. Weight reduction holes 502 may also bemilled in cartridge block 501 in some embodiments to reduce the weightof cartridge block 501. Weight reduction holes 502 are shown forillustrative purposes only; any appropriate configuration of holes maybe formed in a cartridge block to reduce the weight of the cartridgeblock while maintaining the overall structural rigidity of the cartridgeblock that is necessary for the screening process. The paste cartridgeattachment nipple 503 may be made from a metal such as stainless steelin some embodiments.

FIG. 6 illustrates an embodiment of an MLC screening assembly 600including a cross section of a cartridge block 601, a paste cartridge603, a pneumatic fitting 602, and a nozzle 608. Pneumatic fitting 602attaches to the top of paste cartridge 603, and acts to pressurize thepaste in paste cartridge 630 and force the paste out of the cartridge603 and into the paste routing section of the cartridge block 601.Pneumatic fitting 602 may comprise a quick-connect pneumatic fitting.Past cartridge 603 may comprise a cylindrical plastic paste cartridgefilled with a conductive paste (such as a copper paste) for MLCscreening; the paste cartridge 603 may be used to store the conductivepaste after manufacture. Paste cartridge 603 attaches to paste cartridgeattachment nipple 604, which is attached to threaded cartridgeattachment 605. When pneumatic fitting 602 pressurizes and forces pasteout of paste cartridge 603, the paste travels from paste cartridge 603via paste cartridge attachment nipple 604 and threaded cartridgeattachment 605 through hole 606 and flared section 607 to nozzle 608.Flared section 607 causes the paste to flare out and fill a screeningsurface of the nozzle 608. The paste is then screened onto a ceramicsubstrate through the nozzle 608. The dimensions of flared section 607are commensurate with the dimensions of nozzle 608. Nozzle 608 may be acarbide rod nozzle in some embodiments.

FIG. 7 illustrates an embodiment of a method 700 of MLC screening usinga cartridge block and a paste cartridge. FIG. 7 is discussed withreference to FIG. 6. In block 701, the paste cartridge 603 is attachedto the paste cartridge attachment nipple 604. In block 702, the pastecartridge attachment nipple 604 is attached to the threaded cartridgeattachment 605 in the cartridge block 601. In block 703, the pneumaticfitting 602 is attached to the top of the paste cartridge 603. In block704, the conductive paste in the paste cartridge 603 is pressurizedusing the pneumatic fitting 602, such that the paste is forced throughthe hole 606 and flared section 607 of the cartridge block 601 to thenozzle 608. In block 705, the paste is screened onto a multilayerceramic via the nozzle 608. The screening may be performed in order to,for example, fill a via hole in the multilayer ceramic, or form aconductive circuit pattern on the multilayer ceramic.

The technical effects and benefits of exemplary embodiments includeincreased throughput for an MLC screening process, through eliminationof paste transfer from a cartridge to a specialized screening tube, andalso reduction of maintenance and cleaning time for the screeningapparatus.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a”, “an”, and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

The corresponding structures, materials, acts, and equivalents of allmeans or step plus function elements in the claims below are intended toinclude any structure, material, or act for performing the function incombination with other claimed elements as specifically claimed. Thedescription of the present invention has been presented for purposes ofillustration and description, but is not intended to be exhaustive orlimited to the invention in the form disclosed. Many modifications andvariations will be apparent to those of ordinary skill in the artwithout departing from the scope and spirit of the invention. Theembodiment was chosen and described in order to best explain theprinciples of the invention and the practical application, and to enableothers of ordinary skill in the art to understand the invention forvarious embodiments with various modifications as are suited to theparticular use contemplated.

The invention claimed is:
 1. An assembly for screening a multilayerceramic with a conductive paste, comprising: a paste cartridgecontaining the conductive paste; a cartridge block, a top of a cartridgeblock being configured to receive the paste cartridge, the cartridgeblock comprising a paste routing section, the paste routing sectioncomprising a flared section located at a bottom of the cartridge block;a pneumatic fitting attached to the paste cartridge, the pneumaticfitting configured to pressurize the conductive paste in the pastecartridge such that the conductive paste is extruded from the pastecartridge into the cartridge block through the paste routing section ofthe cartridge block by the pressure from the pneumatic fitting; a nozzleconnected to the flared section of the cartridge block, the nozzleconfigured to receive the conductive paste from the flared section, andscreen the conductive paste onto the multilayer ceramic through thenozzle; and a paste cartridge attachment nipple, wherein a top side ofthe paste cartridge attachment nipple is configured to attach to thepaste cartridge, and a bottom side of the paste cartridge attachmentnipple is configured to attach to a threaded cartridge attachment on thetop of on the cartridge block.
 2. The assembly of claim 1, wherein thepaste routing section further comprises a hole located between thethreaded cartridge attachment and the flared section.
 3. The assembly ofclaim 1, wherein the paste cartridge comprises a cylindrical plasticpaste cartridge.
 4. The assembly of claim 1, wherein the cartridge blockcomprises stainless steel.
 5. The assembly of claim 1, wherein thenozzle comprises a carbide rod nozzle.